In many industrial and biological environments, it is desirable to determine the characteristics of fluid internal to fluid systems without breaching the fluid-containing vessel. For example, it is desirable to measure blood pressure characteristics at various points in the organs and blood-carrying vessels without having to breach an organ or vessel surgically to place a pressure sensor directly in the fluid contained therein.
As one example, the assessment of patients with congestive heart failure (CHF) following cardiac surgery remains difficult. For up to six months following surgery, these patients undergo a complex shift in their fluid-volume status. In the outpatient setting, the management of these patients has been performed by a history of increasing shortness of breath and a physical examination entailing assessment of the extent of pedal edema. Currently, these measurements are indirect surrogates of a poorly functioning heart and do not provide objective data on cardiac hemodynamics including heart filling pressures and cardiac output. Another test commonly used to evaluate CHF is a chest X-ray. Unfortunately, this test also does not provide objective hemodynamic data. A Swan-Ganz catheter does provide cardiac hemodynamics and is routinely utilized during and immediately following cardiac surgery. However, it is unreasonable to perform this procedure on a routine basis in the outpatient setting for the necessary adjustment of medications related to CHF because of the danger and discomfort to which the patient is subjected. To date, there is very little non-invasive objective hemodynamic or cardiodynamic data following cardiac surgery that guides the proper management in this complex group of patients.
The availability of an implantable device with the capability of safe, non-invasive hemodynamic monitoring has the potential to change the landscape in the management of patients following cardiac surgery. Availability of such a device would greatly enhance CHF management, patient lifestyle and reduce unnecessary hospitalizations and costs to society, currently estimated at $38 billion/year. Moreover, the potential for life-long in-hospital and outpatient monitoring of these patients may significantly decrease risks associated with invasive hemodynamic monitoring and allow more succinct tailoring of heart failure medications. Furthermore, with a portable monitoring system, patients can be monitored at home, negating costs associated with readmissions and emergency room visits for patients with heart failure.